Along the stretch of U.S. highway where I live, there is a small sign announcing that the road has been "adopted" by the John Birch Society. This fringe group of yesteryear -- whose Dallas members distributed commie-baiting "Wanted for Treason" leaflets of President Kennedy prior to his visit and assassination there -- now sponsors litter removal like any other proper civic-minded organization. The Red-under-every-bed zealotry that Richard Hofstadter dissected in "The Paranoid Style in American Politics" and Bob Dylan satirized in "Talkin' John Birch Paranoid Blues" has been rehabilitated. Or maybe it's just been coyly rebranded, given a veneer of halfway respectable populism by the grass-rootsy Tea Party label, as an outlet for "angry minds" who get to cherry-pick among speculations that the president of the United States is a socialist traitor, a foreign agent/illegal immigrant, a secret Muslim, a tool of Jewish bankers, a black Hitler or all of the above.

The sources of such loopy emanations can be partly gleaned from David Aaronovitch's "Voodoo Histories: The Role of the Conspiracy Theory in Shaping Modern History." With a nod to Hofstadter, but casting a wider, fuzzier net, "Voodoo Histories" runs the gamut from "The Protocols of the Elders of Zion" -- the anti-Semitic mother of all modern conspiracy-mongering -- to the relatively benign crackpottery of "The Da Vinci Code" and its fraudulent inspiration, "Holy Blood, Holy Grail." Aaronovitch sets out to discredit junk knowledge, urban apocrypha and a slew of bunko artists: the con men and fantasists behind the disinformation and fake cabals. He also debunks charges Franklin Delano Roosevelt instigated or acquiesced to the bombing of Pearl Harbor, "Truther" assertions that the second Bush administration likewise carried out or at least permitted the Sept. 11 attacks, and claims that the Clintons operated as a de facto crime family -- the Sopranos of 1600 Pennsylvania Ave.

But if Aaronovitch does a decent job of exposing the lies underpinning these jerry-built myths, his peevish, plodding common sense is hardly a match for the burning near-religiosity that not only makes a Communion wafer of JFK's assassination, but also extends to the overdose death of one-time Kennedy paramour Marilyn Monroe. It's a writhing snake pit of incestuous connections: Did the mob whack Kennedy as payback, or stage the troublesome Monroe's death as a favor to the Kennedys? Was Oswald a brainwashed tool of the KGB or the CIA, a convenient patsy for the Cubans (either pro- or anti-Castro) or the Texans? How many sharpshooters could fit on a grassy knoll? (What about Monroe's ex-husband Joltin' Joe DiMaggio as the second gunman? A man who'd had a 56-game hitting streak certainly would have the eye-hand coordination for the job.) Excavating the visceral, reductive urges of the "I want to believe" mind-set -- the need to translate everything into the neat pieces of some gigantic X-File -- isn't Aaronovitch's strongest suit.

Scanning the milieu of "government by hallucination," Francis Wheen's "Strange Days Indeed: The 1970s: The Golden Age of Paranoia" more effectively captures how conspiracy theories and botched conspiracies such as Watergate entered the collective psyche. Throughout the decade, dark mutterings and dreadful events, like a backdoor form of pop culture, seemed to mutually reinforce everyone's worst suspicions. Moving at a detoxified Hunter Thompson clip, Wheen's travelogue frames the 1970s as an era of institutional collapse, unstable officials, general irrationalism (widespread interest in UFOs, psychic phenomena, mad cults) and terror: the Irish Republican Army's bombing campaign in Britain, the Black September massacre at the Munich Olympics, the Zippy the Pinhead antics of the Baader-Meinhof Gang, and the Symbionese Liberation Army.

Wheen cheekily plays off conceits such as Tom Wolfe's coinage "the 'Me' Decade" and Christopher Lasch's "The Culture of Narcissism," renaming the 1970s the "Them decade." Richard Nixon and his enemies list top the paranoiac charts, of course, lashing out in directions that inevitably intersect with Aaronovitch's voodoo-history practitioners. What Wheen calls "my beloved Watergate" was almost too good and circular to be true -- Nixon's conspiracy to wiretap his foes is ultimately confirmed because he also wiretapped himself, raising the notion of being your own worst enemy to a warped art form.

Equally loaded is the sort of reciprocity "Strange Days Indeed" uncovers between the stalker Arthur Bremer and his target Nixon. A textbook bundle of rage and resentments, Bremer elected to bypass his fixation on "Nixy" and shoot an easier target -- George Wallace -- instead. A hopeless failure even at assassination, the lone gunman still realized his ambition, after a fashion. Like Nixon, he achieved immortality as a symbol; embodying a certain strain of desperate, bitter impotence, Bremer became the inspiration for "Taxi Driver's" Travis Bickle, who in turn inspired John Hinckley Jr., another smudged carbon copy, to take a crack at President Ronald Reagan. Oswald, Bremer, Hinckley: devolution in action, history as a tale told, and made, by idiots.

But what of the people on the real front lines of conspiracy, the professionals trying to detect plots even as their counter-terrorism programs mission-creep their way uncomfortably close to becoming a conspiracy against individual rights? Shane Harris' "The Watchers: The Rise of America's Surveillance State" comes at this dilemma from an unexpected angle: In a fine piece of irony, the author's hero is John Poindexter, a key architect of the post-Sept. 11 surveillance infrastructure, who in an earlier Washington tour of duty was the Reagan security advisor in charge of the Iran-Contra debacle.

Remembering Poindexter from those hearings, where he seemed the very model of an inflexible right-wing "dead-ender," I'd never have picked Poindexter to spearhead massive, highly sensitive intelligence operations. Yet Harris makes a case for him as a more thoughtful, intellectually sophisticated and even technologically visionary figure -- an officer stunned by the 1983 car-bombing of the U.S. Marine barracks in Beirut, so much so that from such a vantage he could already see the writing on the twin towers' walls. Poindexter realized the power of information and quickly grasped that emerging, exponentially multiplying streams of computerized data would transform the outlines of our world far more than any presidency, or any conspiracy.

The most salient thing about "The Watchers" is its feel for the practical reality of intelligence gathering, the operational nuts and bolts of designing and implementing systems that could allow men and women to connect some of the dots instead of merely collecting an infinite and intractably random amount of them. How does someone or something go about isolating particles of genuinely suspicious "transactional information" from the vast indiscriminate ocean of metadata out there? Because the rest of us swim in this ocean too, it becomes imperative that would-be bombers are flagged (none of us wants to end up with our body parts splashed across the evening news) without sucking everyone into the same ominous database for dialing a wrong number or visiting a website or even making a pattern of purchases that might fit some NORA ("Non-Obvious Relationship Awareness") profile.

The challenge for Poindexter, his associates and their teams of "warrior geeks" became to map out "plausible futures" one or two steps ahead of the terrorist curve, beating them to their next move. Scanning horizons for what footprints might be made by disposable cellphones, anonymous e-mail accounts or credit card numbers, they sifted through cyberspace in ways that defied conventional law-enforcement procedures, to say nothing of the Constitution, and made a mockery of traditional, shoe leather-on-the-ground spycraft. Harris is plainly fascinated by their can-do attitude. (He also has a mildly amusing weakness for portentous chapter closings that sound like teasers for next week on PBS' "Frontline.") But he's skeptical of methods that can seem as shadowy and arbitrary as those of the conspirators they track. The great lost opportunity chronicled in "The Watchers" is the "privacy appliance" Poindexter imagined, a way of mining data while shielding individual identities:

[It] would lock private information away in a kind of electronic safe that might only be opened upon order of a judge. The judge would have to find that the government had a reason for thinking this anonymous person might actually be a terrorist. Poindexter called this case-by-case approach to putting names to data "selective revelation."

That's almost utopian, coming from a hardened old hand like Poindexter, but the intelligence community jettisoned the "selective revelation" part of his program in favor of its overarching original designation: "Total Information Awareness," the all-seeing, all-prying eye of a surveillance state composed of black ops (and black eyes) that is potentially watching everything but still missing so many pieces of the big picture. This naturally makes people nervous and feeds conspiratorial thinking, yet what's either most reassuring or most unnerving about "The Watchers" is that the men and women it depicts don't appear to have hidden agendas. For them, technology and not ideology is the overriding concern, a matter of leveling the playing field and harnessing the Internet into one unlimited search engine. The unintended consequences are still rippling into the future, but it's a good bet the warrantless searches and executive orders will leave a scorched legacy that smells a lot like collateral damage.

Of course, conspiracy buffs can only be disappointed in these Watchmen: They seem far removed from the ruthless, implacable uber-spies prepared to orchestrate internal coups, domestic assassinations or even a "digital Pearl Harbor." Poindexter, for all the brilliance Harris ascribes to him, supervised the boondoggle of Iran-Contra. Watergate revealed Nixon not just as a vengeful crook but also as a hapless paranoid. The problem with conspiracies, like everything else, is that they are dependent on human actors, with all their frailties and neuroses and baggage. (The believers are deadlier than the believed-in.)

Things fall apart; the command-and-control center cannot hold. Unless you believe that everything from the Bay of Pigs to the Iraq disaster was designed to fail, thus throwing us off the scent of the Real Killers; then maybe O.J. was telling the truth after all.

Hampton is the author of "Born in Flames: Termite Dreams, Dialectical Fairy Tales, and Pop Apocalypses."